WASHINGTON – Plans for an investigation of whether ex-Rep. Randy "Duke" Cunningham compromised intelligence are inadequate, the top Democrat on the House Intelligence Committee said Thursday.

California Rep. Jane Harman, D-Venice, said Intelligence Committee Chairman Pete Hoekstra, R-Mich., should use outside, nonpartisan or bipartisan staff for the probe of Cunningham's work on the committee.

"The chairman's decision to use existing committee staff to review this issue threatens to compromise our ability to conduct a thorough, expeditious and bipartisan investigation of the Cunningham matter," Harman said in a statement. "Dedicated temporary staff with extensive investigative experience and appropriate security clearances must be hired ... Existing staff cannot be expected to investigate their bosses."

Cunningham, a California Republican who resigned from Congress last month after admitting taking $2.4 million in bribes from defense contractors and others, had served since 2001 on the Intelligence Committee, and since this year as chairman of the panel's subcommittee on terrorism and human intelligence.

Hoekstra announced shortly after Cunningham's resignation that he had asked committee attorneys to review Cunningham's work on the panel to ensure he didn't improperly influence committee actions or decisions.

"The form that this inquiry is going to take is something that is still being discussed by the chairman and ranking member," Hoekstra spokesman Jamal Ware said Thursday. "The chairman is not willing to play this inquiry out in the press."

Meanwhile, Gov. Arnold Schwarzenegger on Thursday set an April 11 special election to replace Cunningham. If no candidate wins a majority in the primary, the top vote-getters in each party will face off June 6, the date of a statewide primary.

County officials had asked Schwarzenegger set the April 11 special election to consolidate the possible run-off election and save the county $1.3 million.

Several candidates have announced their candidacy for the seat in the heavily Republican district, including former San Diego-area Rep. Brian Bilbray; former state Sen. Bill Morrow and former California Assemblyman Howard Kaloogian. Democrat Francine Busby, who lost to Cunningham in 2004 by 22 percentage points, is also running again.